Re: Refresh-avoidance

Of the responses you've received Dave, there are a lot of problems that you should be aware of. 1) The suggestion of a page processing the transaction,and then using redirection to move to a final "Thank-you page" does not work, so don't try it. In this type of scenario, if you do a reload on the browser while on the thank-you page, it knows enough to skip the intermediate redirect page, and will attempt to resubmit the form from the original page. 2) All the db suggestions that tell you to do a check first, or a replace into, are valid if and only if you can do a db lock (e.g. a "BEGIN" transaction statement) to ensure the database isn't being changed half-way through (ala user submitting twice in rapid succession, and having two PHP scripts concurrently trying to add the exact same user). The best solution to this problem IS at the database end. But the trick is to make use of what is known as an atomic transaction that will do what you need. For example, if your userids must be unique in the database, then use the database to create a unique primary key index on this userid. This means that when you add a record into the database, the database will automatically reject it if the userid already existed, and you can then handle the response appropriately. Note...you don't do a "scan" and then "insert", you just plainly issue the insert, and rely on the db to reject duplicates. By doing the above, you've created a solution that not only solves the reload problem, but ALSO address different users happening to pick the same userid. Thomas David VanHorn wrote: > > I have a form issue that's bugging me. > As a part of a user signup, there is a page with a form. > The user fills out the form and submits, and all is well, and he gets a > confirmation screen, but if he refreshes the confirmation screen (this page > contains the script that does the signup work) then a duplicate account is > created. > > I know I can scan for dupes and abort, but is there a simpler way to avoid > this? > (Like a "refresh-killer"?) > > TIA > -- > > www.SpamWhack.com A pre-emptive strike against spam > A tornado is a lady whose skirts you do NOT want to look up! > Where's dave? > http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, e-mail: php-general-unsubscribe@lists.php.net > For additional commands, e-mail: php-general-help@lists.php.net > To contact the list administrators, e-mail: php-list-admin@lists.php.net -- ------------------------------------------------------------ Thomas Reinke Tel: (905) 331-2260 Director of Technology Fax: (905) 331-2504 E-Soft Inc. http://www.e-softinc.com Publishers of SecuritySpace http://www.securityspace.com